The present invention relates a high-frequency incision instrument for an endoscope. A high-frequency incision instrument for an endoscope is used for incision of in vivo mucosa and the like. The high-frequency incision instrument is generally inserted through an instrument channel of the endoscope. Typically, the high-frequency incision instrument is configured such that a rod electrode provided at a tip end portion of a flexible sheath is operated to protruded forward or retracted from the tip end of the sheath by an operating unit connected to the proximal end of the sheath.
Depth of the incision of the in vivo mucosa depends on a condition of a target portion and/or operational conditions of the high-frequency incision instrument, it is preferable that the depth is adjusted to be safe and optimum amount for the target portion by adjusting a protruding amount of the rod electrode. An example of such a configuration is disclosed in Japanese Patent Provisional Publication No. P2002-113016A (hereinafter, referred to as '016 publication).
According to the invention disclosed in '016 publication, stoppers configured to abut against each other are provided to the tip end of the sheath and the proximal end of the rod electrode, respectively, and a position of a cap member screwed onto the tip end of the sheath is adjusted so that the maximum protruding amount of the rod electrode with respect to the tip end of the sheath is restricted.
When in use, the high-frequency incision instrument is inserted through the instrument channel arranged inside an inserting section of the endoscope. Since the inserting section is bent inside a human cavity, the cap member screwed onto the sheath may be rotated when the high-frequency incision tool is inserted through such an instrument channel, and the adjusted condition of the protruding amount of the rod electrode may be changed. In the worst case, the cap may be disengaged from the sheath inside the human cavity.